EARNINGS PER SHARE - Basic earnings per share of common stock (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Basic and diluted earnings per share:
Net income	$ 605,522	$ 439,045	$ 1,059,823	$ 1,172,199
Weighted average common shares outstanding (in shares)	2,823,271	2,809,834	2,819,952	2,806,341
Basic and dilutive net income per share	$ 0.21	$ 0.16	$ 0.38	$ 0.42
Options outstanding	0	0	0	0